The fine structure of the membrane of cell organelles appearing in the atypical spermatid of Cipangopaludina malleata Reeve has been studied in thin sections by an electron microscope.
The porous structure has been revealed in the wall of the flattened sacculus consisting the Golgi complex. The walls are calculated 35 A thick. The mitochondria consist of a small number of tubules and an osmiophilic matrix. The mitochondria represent a complex system of tubules projected from the inner layer of the limiting membrane, and the tubules consist of double dense mcmbrans involving a less dense interspace. The mitochondria aggregated along the developing tail filaments coalesce to form an elongated mass of relatively large size. The limiting membrane of the rough-surfaced endoplasmic reticulum appears apparcntly to be a single layer, which makes its appearance in the area where the tail filaments devlop. The smooth surfaced endoplasmic reticulum is bordcrcd by a double layercd membrane consisting two opaque layers with a less opaque interspace. The vesicles containing dense granules, which represent the smooth surfaced endoplasmic reticulum, migrate to the cell periphery. The smooth surfaced endoplasmic reticulum scems to function as an intraccllular conductor.